Plate straightener



Dec. 22, 1936.- F. T. POWERS PLATE STRAIGHTENER Original Filed Jari. 28,1932 Patented Dec. 22, 1936 UNITED STATES PATENT ()FFICE ApplicationJanuary 28, 1932, Serial No. 589,399 Renewed June 1, 1936 '3 Claims.

My invention relates to the art of making printing plates byphoto-mechanical processes, and particularly to a novel and usefulmechanism for straightening plates which have become bent,

twisted or warped during the process of powdering and etching.

Objects and advantages of the invention will be set forth in parthereinafter and in part will be obvious herefrom, or may be learned bypractise with the invention, the same being realized and attained bymeans of the instrumentalities and combinations pointed out in theappended claims.

In the process of etching half tones or line cuts it is customary toheat the plates to set the powdered dragons blood, which is commonlyused as a resist to protect the shoulders of each successive bite, toprevent undercutting and to permit carrying the etching process to asufficient depth 20 to insure satisfactory printing quality. Thisheating process is immediately followed by a quenching or coolingprocess which usually con sists of bringing cold water into contact withthe back of the plate. During these heating and cooling processes theplate is subjected to such a wide range of temperatures that the platebecomes warped and twisted or curled. The result is that the plate doesnot lie flat on a cooling surface nor will it present a plane, flatsurface to the action of powdering brushes in an automatic powderingmachine. Another factor which also contributes to the bending of theplate is the fact that when the powdering process is carried out by handthe operator commonly uses a pair of pincers or pliers to handle the hotplate from the heater to the cooler. By means of these pliers grippingthe edge of the plate it is lifted and moved from the heating device tothe cooling device. This operation has a marked tendency to bend theplate along the edge gripped by the pliers. When the plate is powderedin an automatic powdering machine, such as is described in my co-pendingapplication Serial Number 513,364, filed February 4, 1931, it isimportant that the plate be kept straight and flat, so that it willreceive a uniform action of the powder brushes over its entire surface.

Heretofore, the method commonly employed by skilled workmen to flatten awarped or bent plate has been to slam the bent or warped plate violentlyagainst a flat surface, such as a table top or a slab of lithographicstone, or the workman may bend the plate with his hands, or by utilizingthe edge of a table or other convenient object he may bend the plate inan effort to flatten it.

Such methods are at best crude and inaccurate and not always productiveof satisfactory results even in the hands of a skilled and experiencedworkman.

By my invention I provide a mechanical means whereby warped or bentplates may be automatically straightened or flattened more accuratelyand in less time than is required to perform the operation by hand.

In the accompanying drawing, I have shown a preferred embodiment of myinvention, which, taken together with the description, will serve toexplain the principles and method of operation of my invention.

Fig. 1 is a vertical sectional elevation of the apparatus on itslongitudinal median line. Fig. 2 is a section on the line 22 of Fig. 1.

In the drawing like characters are used to designate the same or similarparts and arrows indicate the direction of movement or rotation.

In the drawing, two pairs of sprocket wheels, I and 2, only one of eachpair being shown, are mounted on shafts 3 and 4 respectively, operatingin suitable bearings 5 and 6. A pair of detachable link chains I, one oneither side of the mechanism, cooperate with the pairs of sprockets Iand 2. Attached to these chains at suitable intervals are a plurality ofcross bars, 8, the ends of which are attached to suitable attachmentlinks in the chains I. Between the chains I and under the cross bars 8and supporting them, is a plurality of grid bars, 9, extendinglengthwise of the apparatus parallel to the chains. These grid barsterminate at the sprocket wheels I and 2, thus permitting the crossbars, 8, to be carried around the sprockets without interference.Mounted about midway of the apparatus and below the grid bars, 9, is ashaft, II], which is movable vertically by means of the adjustablebearing, II, which may be raised or lowered by means of the screws, I2,in the guides, I3. Upon the shaft, II], are mounted a plurality ofrollers, I4, which are located between the grid bars, 9, and which attheir uppermost portion project above the tops of the grid bars. Theamount of such projection is susceptible of regulation by means of thescrews, I2. Above the grid bars, 9, are rigidly mounted on shafts I5 andI6 operating in bearings, I1 and I8, respectively, two rollers, I9 and20, each provided with sprocket wheels 2I and 22, respectively, whichare also rigidly mounted on shafts I5 and I6 and engage the chains 1. Tothe shaft Ill are also rigidly attached sprockets 23, which also engagethe chains I from their under side.

The rollers l4, l9 and 20 are each provided with pockets or depressions,24, in their periphery extending lengthwise the full length of therollers. The circumference of the rollers, l4, l9 and 20, are equal tothe spacing of the cross bars, 8, and the number of teeth in thesprocket is equal to the number of links in the chains 1 betweensuccessive cross bars, 8, so that a movement of the chains, I,v adistance equal to the spacing of the cross bars and the consequentrotation of the rollers, I4, [9 and 20 by the sprockets 2|, 22 and 23,produces exactly one revolution of the rollers. The timing of each ofthe rollers and the position of the pockets, 24, is such that thesepockets always coordinate with and receive the cross bars, 8, thuspermitting the cross bars to pass the rollers without interference. Atthe delivery end of the chain conveyor, 1, is a receiving table, 25,spaced apart from the ends of the grid bars, 9, to permit the passage ofthe cross bars around the sprockets 2. 'Motive power may be derived fromany convenient suitable source, such as a motor, 26, cooperating withbelt, 21, and pulley, 28, attached to shaft, 4. The entire mechanism issuitably mounted on a supporting framework.

The operation of the mechanism is carried out i as follows: The bent orcurled plate to be straightened is placed in position 13 on top of thegrid bars, 9', between two of the-cross bars, 8, either before or afterthe apparatus has been started in motion. The next succeeding cross bar,8,

' comes into contact with the trailing edge of the plate andslides italong on top of the grid bars under the roller, l9, Whose peripheralsurface is moving at exactly the same speed as that of the plate andconsequently contacts with the upper surface of the plate without anyrelative motion occurring between the two surfaces and, therefore, thereis no rubbing or scratching of the surface of the plate by the roller.As the plate is pushing forward by the cross bar, 8, its advancing edgemeets and is flexed or bent slightly upward by the rotatingunder-roller, M. The amount of the upward bending or flexing actioncaused by roller I4 is under the control of the operator by adjustingthe height of this roller by means of the adjusting screws, l2. As theplate advances further, its advancing edge meets and is fie'xeddownwardly or in a direction the reverse of its previous bending by therotating roller, 20. As the plate is still further advanced by the crossbar, it again contacts with the top of the grid bars, 9, and is againslightly flexed in the reverse direction. As the plate is furtheradvanced it is pushed onto the receiving table, 25, into position C, asthe cross bar travels around the sprocket, 2, on its circuit. It isobvious that any number of plates may be passed consecutively throughthe apparatus when placed one at a time in position B betweenconsecutive advancing cross bars. In

its travel under and over the three rollers, each plate is given threeslight reversals of bending with the result that with the roller, 14,properly adjusted as to its height, the plate comes out of the operationin a substantially flat plane condition, and is ready for any subsequentoperation.

My new apparatus is equally adaptable for use.

as a separate machine for performing the single operation ofstraightening plates, or for incorporation in a mechanical powderingmachine, as an integral part thereof, such, for example, as my automaticmechanical powdering machine described in my co-pending application,serial number 513,364, filed February 4, 1931, in which I find my newdevice particularly effective in keeping the'plates fiat and in a propercondition forreceivingthe various operations applied to them.

It will be obvious that my invention may be reduced to practice in avariety of forms other than that shown and described herein, withoutdeparting from its spirit and I do not wish to be understood as limitingmyself except as set forth in the claims.

I claim: I

1. A device for straightening photo-mechanical printing plates,comprising in combination three or more parallel rotatable cylindricalrollers, successive rollers being positioned on opposite sides of thepath of travel of the plates, aportion of them being entirely on oneside of a plane and the remainder predominantly but not entirely on theother side of the same plane, means for varying the position of aportion of said rollers,

travelling means for conveying the plates bev tween successive rollers,and means for rotating said rollers at a peripheral speed equal to thespeed of the plate.

2. A device for straightening photo-mechanical printing plates,comprising three or more cylindrical rollers of similar diameter, havinglongitudinal depressions in their periphery, positioned to flex theplates as they pass between adjacent rollers, conveying means forpassing the plates between said rollers including a plurality of crossbars spaced apart a distance equal to the periphery of said rollers, andtimed to coordinate with said depressions, means for driving saidconveying means and said rollers at identical lineal and peripheralvelocities respectively.

3. A device for straightening photo-mechanical printing plates,comprising three or more cylindrical rollers of similar diameter, havinglongitudinal depressions in their peripheries, positioned to flex theplates as they pass between adjacent rollers, and conveyng means forpassing the plates between said rollers, including a cross bar timed tocoordinate with said depressions.

FRANK T. POWERS.

